1. Field of the Invention
The present invention relates to an electromagnetic apparatus for displacing a valve element by attracting a movable core to a fixed core under electromagnetic forces generated when a solenoid coil is energized, or for moving a movable member by attracting the movable core to the fixed core under the electromagnetic forces.
2. Description of the Related Art
Heretofore, there have been used in the art electromagnetic valves having a valve element which is displaced by attracting a movable core to a fixed core under electromagnetic forces generated when a solenoid coil is energized.
For example, Japanese Laid-Open Utility Model Publication No. 63-56371 discloses an electromagnetic valve having a movable core which is coated on its entire surface with a nonmagnetic, highly wear-resistant thin film for the purpose of minimizing reduction in the flux density of the magnetic circuit.
However, because the thin film is applied to the entire surface of the movable core which has a certain diameter, the outside diameter of the movable core of the disclosed electromagnetic valve is increased by the thickness of the thin film. Consequently, not only the outside diameter of the movable core, but also the thickness of the applied thin film needs to be controlled with care.
Furthermore, it is necessary to prevent the thin film applied to the entire surface of the movable core from peeling off or swelling.